D.B.
Your job as a parent is to give your daughter the skills and confidence to face rejection, mean talk, and things not going her way.
It is not to intervene every time some kid is mean or says "You're annoying." Maybe your daughter IS annoying, and you'd have no way of knowing! Sure, we all see the best in our kids, and we see a very small percentage of their interaction with other kids. So we can't tell if their version of events is realistic.
So sometimes kids have to be disappointed, they have to face immature or nasty people, and they have to shake it off and deal with it. They can be taught to avoid consistently mean people, but they also have to be taught how to be resilient in the face if disappointment and unfairness. They will have this at 5, 7, 11, 15, 18, 25 and 46.
Your job is to be her sounding board but not to get too involved. The more she thinks that every slight is a reason to sit and mope and feel crappy, the less strength she will have to figure out what to do about it. If someone is consistently mean, she can walk away. She will learn to define "friendship" and learn that she cannot change everyone, only her own reaction to them.
This is a good strength to have when it comes to teachers in high school, college professors, bosses, and much more.
Resist the urge to protect your child from every hurt. They need to fall down sometimes and get bruised, and they can't spend their lives in a play pen, right? Same thing when it comes to relationships. Instead of trying to protect her from everything, work on helping her prioritize things and become more resilient.